Liquid crystal displays (LCDs) are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images with little power but are also very thin. The liquid crystal molecules in an LCD do not emit any light themselves. The liquid crystal molecules have to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module for an LCD is generally needed. A prism sheet is generally needed in a backlight module for improving a brightness of the backlight module.
Referring to FIG. 7, a conventional prism sheet 70 includes a substrate 72 having a plurality of prism structures 74 integrally formed at a light output surface thereof. The prism sheet 70 can gather light beams to improve a brightness of an associated backlight module (not shown). However, the prism sheet 70 generally needs to cooperate with a diffusing sheet (not shown) in order to provide uniform light beams, which adds to the overall thickness and the cost of the backlight module.
Referring to FIG. 8, another conventional prism sheet 80 includes a plurality of prism structures 82, a substrate 84, and a diffusing layer 86 arranged in that order from top to bottom. The diffusing layer 86 includes a plurality of diffusing particles 861 formed therein, which enables the prism sheet 80 to uniformly emit light beams out from the prism structures 82. However, the diffusing layer 86 is generally a structure formed separately from the substrate 84, and therefore adds to the overall thickness of the prism sheet 80.
What is needed, therefore, is a prism sheet that can overcome the above-described deficiencies.